I think at this stage you should keep experimenting, trying and testing materials, colors and textures. I am sure after a bunch of trials your building will germinate and look fantastic. Good thing you have a 3D model to do this with, the sky is the limit here.

Texture is always good, perhaps some metals? Not sure where the building is or what you are going for. For the interior I have some art I have recently completed that would look awesome and make a nice statement. I also do commission work. I have recently completed some that would look great. All are original acrylic paintings on heavy gallery wrapped canvas. Please contact me at julie@jul313.com for further info or check out my website at www.jul313.com.